Although 32-bit microcontroller unit volumes are still small in comparison to 4-, 8- and 16-bit MCU volumes, they represent the fastest-growing segment of the MCU market. In a 1995 report, the market research group Information Architects predicted that 32-bit MCU sales would grow to 150 million units in 1997, representing an increase of more than 230 percent in four years. Moreover, sales volumes for 32-bit devices are disproportionately large for their unit volumes because of their inherently high value, reflecting the greater profit potential of 32-bit systems.
Outside of the PC industry, which is locked into the x86 architecture, embedded applications represent the largest potential market for 32-bit systems. Key areas for growth of 32-bit microcontrollers include:
As an active ARM licensee, TI has licenses for several cores. Among these, one core TI has implemented is the ARM7TDMI with the Thumb extension. This core is the smallest in the ARM family, helping minimize expense and leaving space for a number of peripheral functions on the same die.
Even though RISC CPUs are perceived as being hungry for memory, the ARM cores are in fact among the most code-efficient in the industry, requiring approximately 30 percent less code than competing architectures and providing industry-leading MIPS/watt performance. The Thumb extension, in particular, addresses the issue of conserving memory by providing two independent RISC instruction sets for improved code efficiency. While 32-bit instructions are available for fast execution, an alternate set of 16-bit instructions can be used for high code density. The 16-bit instructions are expanded at run time into 32-bit instructions, which are then executed with no performance loss by the full-32-bit ARM internal architecture. Unlimited alternation between the instruction sets is allowed in programming. For the memory space and cost constraints of embedded systems, the ARM core with the Thumb extension provides an optimum combination of high performance and cost efficiency.
The TMS470 design has a debug module embedded in the core CPU, allowing debugging during development or in a production cycle. The module provides breakpoint, read and write registers, so that an external monitor can implement all common debug functions. The module is accessible through an integrated IEEE 1149.1 (JTAG) serial test bus.
While an ASIC methodology and CPU core lend themselves to semicustom designs, they also allow TI to respond to market needs quickly and flexibly with catalog and application-specific components. From the OEM perspective, catalog components support new product designs when volumes are small and availability is key. Later, for subsequent product generations with higher volumes, migration to application-specific components created by TI can help simplify design and reduce development times. Finally, for selected high-volume designs that are highly integrated for cost efficiency, full-custom components are possible.
The CPU core is very small, requiring only 3 square mm on the silicon die in the 0.35-micron implementation, and 2 square mm in the 0.25-micron implementation. It is optimized for low-voltage operation, with power estimated to be 0.52 mA/MHz at 3.3 volt and 40 MHz. Operating frequencies of up to 70 MHz are planned. Further power efficiencies in product designs will be enabled as new process nodes are coupled with power management functions that turn off individual functional blocks when they are not in use.
Peripheral functions that are currently available or are in development include clocks and timers, DMA controllers, bus controllers, interrupt controllers, serial channels, RAM and others. In addition, TI is working on a selected set of peripherals drawn from its experience in designing microcontrollers for embedded applications. These are being created to meet a variety of user requirements, such as throughput, address space, cost, power consumption, etc.
In addition, TI's other technologies can be added as application needs require. These technologies include DSP cores, analog/mixed-signal functions and high-performance memories. SRAM and Flash memories both require advanced process technologies for integration in high-performance CMOS. TI has developed these technologies and is prepared to use them in product design as market demand dictates.
Access to TI's large inventory of designs can help shorten development cycles from man-years to man-months. Examples of the many specialty designs that can be quickly adapted to the RISC architecture are timers developed to meet the exacting specifications of automobile engine control and LAN controllers created for automotive networks.TMS470 microcontrollers are supported by two sets of development tools. On the one hand, TI supplies its own TMDS470 set of software tools, similar to the TMS370 tools. These include an efficient C compiler, assembler-linker and a simulator-emulator allowing debugging of code for TMS470 devices. The TI tools operate on Unix workstations and on a PC using a DOS-based windowed environment. When the 32-bit microcontroller core is combined with other TI products, such as DSPs, other processors, compression cores or networking products, the development environment serves as a common platform and ensures that different elements will work together efficiently.
The other set of development tools is the Development Toolkit 200, licensed from ARM and made available by TI. Toolkit 200 also includes a C compiler, assembler-linker and simulator. It operates on Unix workstations and on a PC using a Windows-based environment. Because this set of development tools is open to all ARM licensees, third-party support is available and growing. Contracts with tool suppliers such as WindRiver Systems, ISI and Microtech exist for real-time operating systems and with Lauterbach for in-circuit emulation capability.
The XDS510, a TMS470 emulator that is compatible with both tool sets, supports development with a non-intrusive scan approach through the IEEE 1149.1 (JTAG) bus. Scan capability provides the programming hooks for total accessibility, visibility and controllability of all programming structures on-chip without the need for such high-cost modifications as bus expansion or high pin counts. The emulator offers source-level debug in C and assembly languages, benchmark execution of code, real-time breakpoint analysis, non-real-time performance profiling, multiprocessor debug and other programming tools.
Experience in embedded applications has taught TI how to build microcontrollers to meet multiple requirements, such as footprint, specialized functions, low power, cost and performance. TI's broad line of products, wide variety of processes, and integration technologies make the company unusual in its capability to create new types of microcontroller products that meet the rapidly emerging market needs of embedded systems.
Trademarks:
Thumb is a trademark of Advanced RISC Machines, Limited.
Windows is a trademark of Microsoft Corporation.
Texas Instruments Enhances Customizable IC Capabilities With 32-Bit ARM Microcontroller Core - News Release
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